This invention relates to a floppy disk with a rigid outer shell that encases a magnetic disk, and more particularly to a floppy disk in which the magnetic disk rotates in contact with a liner made of nonwoven material attached to the inner surfaces of the shell.
A floppy disk is constructed by sandwiching a magnetic disk between two shell halves, the inner surfaces of which have precut nonwoven material liners attached to them. The liner is in contact with, and protects the magnetic disk which rotates inside the shell. To protect the surfaces of the magnetic disk from scratches, as well as to remove foreign particulates on the magnetic disk's surfaces, a liner made of nonwoven material made of extremely fine fibers is used. These nonwoven microfiber materials, which are known and commonly available, are flexible, and can protect the surface of the magnetic disk without scratching it. The nonwoven material is a volumetric collection of randomly oriented fibers which are bonded at fiber crossing points and fabricated into sheets. However, when this nonwoven material is cut into a specified shape, microscopic fibers protrude from the cut edge. After the shell halves have been sealed together and the floppy disk is complete, microfibers protruding from the liner, especially at the lead slot in the liner, become separated by disk rotation, become lodged between the magnetic disk and the read write head, and thereby cause bit errors.
Automated equipment has become particularly prominent in recent years. Various automated cutters are configured to cut such nonwoven material by scissoring between male and female pieces. However, the cutting interval of the male and female pieces of these cutters is wider than the microfibers of the nonwoven material. When cutter sharpness is reduced, fibers are not reliably cut, and this readily causes fibers to protrude from the cut edge. Such nonwoven materials in which the fibers are made from synthetic resins such as rayon, polypropylene, polyester, nylon, or acrylic are conventionally used for the liners. Since the extremely fine fibers of these nonwoven materials are on the order of 10 to 20 microns thick, the cutting interval of the male and female pieces must be made smaller than that. Consequently, very high precision machinery is required for a cutter that can reliably sever microfibers along the cutting edge. Further, since cutter use is accompanied by wear and reduction in sharpness, cutting the liner from such nonwoven material with a consistently good cutting device is very difficult. For this reason, it is extremely difficult to cut reliably and consistently, and to prevent fiber protrusion from the cut edge of the liner.
Further, regardless of how well the cutter operates, when short fiber pieces are cut loose along the cut edge, there is no way to prevent these cuttings from separating from the liner during use after fabrication. In other words, since such nonwoven material is a collection of randomly oriented fibers and the fibers are bent and joined at common crossing points, even for a straight cut, a single fiber can be cut in two places between crossing points with other fibers. Such a fiber has both ends severed from crossing points bonded with other fibers, and it becomes a loose fiber cutting which is not connected to the liner. This fiber cutting may become separated from the liner after disk fabrication, and will usually get caught between the magnetic disk and the read write head, and causes bit errors as a result.
More particularly, since both cut edges of the liner's disk head slot are perpendicular to the direction of magnetic disk rotation, cut fibers at these edges which are not securely connected with the liner are especially likely to become separated, stick to the surface of the magnetic disk, and be carried inside the shell. Fiber cuttings carried inside the shell ultimately end up between the magnetic disk and the read write head to cause bit errors. To avoid this cause of bit errors, the amount of fiber separation occurring at both cut edges of the disk head slot should be drastically reduced.
As shown in FIG. 5, one way to reduce fiber separation is to bond the edge of the disk head slot 5 in the liner 3 to the shell 2, so that fiber separation will not occur at that edge. However, in order to reliably bond the edge of the disk head slot 5 to the shell 3, the liner 3 must be accurately aligned with the shell 2. Any misalignment between the liner 3 and the shell 2 makes it impossible to attach the edge of the disk head slot to the shell. In the actual fabrication process, it is extremely difficult to accurately align the flexible, easily distorted liner with the shell.
The present invention was developed to overcome the problems described above. It is thus the primary object of the present invention to provide a floppy disk that simply and easily reduces fiber separation from the liner, and decreases bit error caused by the separation of microfiber cuttings from the liner.